Muffler



April 9, 1935. c. E. HATHORN MUFFLER Filed May 31, 1932 INVENTOR. (Zar/esflbbilmrzz Patented Apr. 9, 1935 PATENT OFFICE MUFFLER Charles E. Hathorn,

Hempstead, N. Y., assignor to Curtiss Aeroplane & Motor Company, Inc., a corporation of New York Application May 31, 1932, Serial No. 614,316

3 Claims.

My invention relates to heat engines and more particularly to devices for muflling the noise of the hot gas exhausted from heat engines.

An object of the invention is to provide a I compact and emc ent mumer for hot exhaust gases, which by its construction will be inherently well cooled.

An additional object of my invention is to provide a muiiler which by its action will build up 2. minimum of. back pressure in an exhaust sys- A further object of my invention is to provide a muffler which simultaneously reduces the pressure and temperature of the exhaust gases so that a minimum of noise emanates with the gases discharged.

A still further object of my invention is to provide a muffler which may be eflectively used on engines of large displacement, such as aircraft engines, and in the construction-of which its weight will be Another object of the invention is to provide a standardized muffling unit, so that a plurality of such similar units may be assembled in series whereby a muffler may be provided to meet the vices for aircraft engines signs which are partly successful all make -use of well known principles of cooling and pressure reduction of the exhaust gas so that the hot exhaust gas meets the outside air at a low temperature and at a pressure approaching that of the. atmosphere. A principal difliculty, in designing an effective mufller for aircraft engines of large displacement, is to provide a device which will adequately muffle the exhaust noise but at the same time will be compact, light in weight, and so constructed that it offers a minimum of resistance to the e of the aircraft through the air. It has been difficult in the past to attain-adequate coolingof and adequate silencing capacity in the muffler without a redundance'of parasitic surface area exposed to the slipstream of the aircraft.

By the construction of my muffler I am able to rapidly dissipate heat and rapidly reduce exhaust gas pressure by providing a structure which inherently causes the exhaust gases to change direction frequently and to impinge upon a comparatively large but compact surface so that they are adequately cooled.

Further advantages and objects of the invention will be apparent from a consideration of the appended drawing and froma readin of the subjoined specification, which show the present preferred embodiment thereof.

In the drawing, wherein similar numbers indicate similar parts:

ring to Fi 4 of the Fig. l is a side elevation of the invention, partly broken away;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a section on the line 3-3 of 1; and

Fig. 4 is a perspective view of an alternative embodiment of the invention.

Describing my invention in detail, and referdrawing, II' is a complete muiller comprising an entrance conduit Ill, and three muffling units 342' and 43' extending from the conduit l0. Theexhaustgaspassingthrough the muflier leaves the muffler at 2|. the muffling units ll, 42' and 43 are arranged cooling fins 26' which comprise flat metallic strips extending radially with respect tothe muffler axis, and longitudinally along the mufiler. The fins 26' are so formed that their inner edges are complementary to the outer contours of the muffler units ll, 42 and 43'. They likewise form a structural element of the muffler H, by holding the muilling units ll, 42' and 43' in their proper position with respect to each other. The manner inwhich this is accomplished will be described later.

Each mufiling unit ll, 42' and '43 of the muflier H is similar in form and construction. Two such units may be assembled as shown in Fig. 1, three may be used as in Fig. 4, or additional units may be assembled as required.

A detailed description of the unit will likewise describe l2, and the units ll, and 43. The muilling unit 4| comprises an annularly cupped ring it having the diameter opening similar to the outside diameter of the inlet conduit Ill. The inlet conduit in is inserted in the ring it and is fastened thereto. The ring 14 is placed over the inlet conduit it so that its concave surface faces away from the direction of flow of the exhaust gas in the conduit ill. Baflle plates 22 are fastened to the inner cupped portion of the ring ll in a plane parallel to the axis of the ring II, but ofiset angularly from a radius thereof. An annularly cupped disc l2, provided with slots 23 which engage the baffles 22, is placed so that its concave surface faces the incoming exhaust gases from the conduit Ill. The outside diameter of the disc I2 is substantially less than the outside ring ll, but greater than the di ameter of the inlet conduit Ill. The disc l2 may be attachedto the bailles 22 by welding or other suitable means. The baffles 22 thereby form a support, holding the disc 12 in fixed spaced relall (Fig. 1)

tion to the ring It. The disc l2 may have formed therein a central opening 24, or its central portion may be closed as shown by 25 in the otherwise similar disc l3 of the muflling unit 2. A funnel shaped member I5 is attached by welding or other suitable means to the outer periphery of the ring it as at H. The member I6 is so formed that its inner surface provides a smooth continuation of of its Around the contour of the ring I4. The member I6 converges inwardly to the portion I8, which is formed with a radius such that the outer surface of the portion I8 of the member I6 is complementary to the outer surface of the inner portion of the ring I4. By this construction, that portion of the mufiling unit formed by the ring I4 and the funnel member I6 embraces the disc I2. The similarly constructed muflling unit 42 may be assembled on the mutiiing unit 4|, the ring I5 of the unit 42 engaging the portion I8 of the funnel member I6 of the unit 4 I. Additionalsimilar muflling units may be similarly a plied to the unit 42 to build up a mufller having three or more mufiling units.

In the mufiler II, two muflling units 4| and 42 are assembled as above described, The cooling fins 26 span both themutliing units and each fin is formed so that its inner edge conforms with the contour of the muflling units 4| and 42. The fins are arranged in. planes passing through the axis of the muffler I. The fins 26 are attached to the muflier by welding or other suitable means, and

form a structural element of the muffler I I, holdof the ring I4, it encounters the baffles 22.

.the funnel member I6.

ing the mufliing units 4| and 42 in their proper relation to each other.

When additional mufiling units are assembled,

the fins 26 would be formed to span all the mutiling units, as shown in Fig. 4.

The action of the muffler is as follows: Hot exhaust gases under a pressure greater than atmosphericpass from the engine thru suitable piping and enter the muffler by means of the inlet conduit II). ,The path of the exhaust gas in its passage through the muffler is represented by the dotted line 21. The gas, entering the muffler, impinges upon the disc I2. Following the curvature of the disc I2, the gas is diverted radially outwa'rdand then is reversed in its flow. As the gas leaves the disc I2 and impinges upon and follows the contour These, by their radially offset position, impart a spiral motion to the gas. The gas, impinging upon the inner portion of the cupped ring I4, again is diverted radially outward and reversed in its flow,

following along the inner surface of the funnel member I6. The gas is again changed in direction and leaves the mufliing section 4| through the opening formed by the inner portion I8 of Gas leaving the unit 4| immediately enters the unit 42 since it is adjacent to the unit 4|. The passage of gas through the unit 42 is'similar to its passage through the unit 4|.

. In its passage through the muffler, the exhaust gas is frequently reversed in direction and is caused to impinge repeatedly upon the outer surface of the muflling unit. 'Heat is copiously transferred from the gas to the'mufiling unit and the dissipationof this heat from the muflling unit is effected byth passage of air thereover. Likewise, heat'is transmitted to the cooling fins 26 which are likewise cooled by their contact with the outside air. Primarily by adequate cooling of the gases, with consequent reduction in volume,

thepressure of exhaust gas is very materially reduced, so that upon its exhaust into the atmosphere, the pressure and temperature of the gas approach that of the outside air with consequent minimization of noise.

The succeeding stages of the mufliing device as 42' and 43' in Fig. 4 may, if desired, be made smaller in diameter through the fact that the gases in their passage through successive stages become cooler and hence are reduced in volume.

It will be noted that the passage of the gas through the muffler is at all times carried in a smooth path as provided by the smoothly curved surfaces of the disc I 2, the ring I4 and the funnel member I6. This path is at all times free and open, and hence the back pressure caused by restrictions within the mufller is minimized by said free and unrestricted passage of exhaust gas.

It will be seen also that by the repetition of the stages of the muffler, each stage may use the same form of component parts as those used in the preceding stage. This allows for the construction of mufflers for small and large engines simply by increasing the number of mufiling units. Likewise it will be seen that the overall diameter of the muffling unit is only about twice as great as the diameter of the inlet conduit I0, thereby causing only a slight increase in the parasite resistance which the muffler might offer in the flight of an aircraft.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. A mufiling device for engine exhaust gases including an entrance conduit, a series of spaced annularly cupped discs having their concave surfaces facing said entrance conduit, a series of annularly cupped rings, each having its concave surface facing the concave face of one of said discs, substantially funnel shaped member joining the outer periphery of each of said rings with the inner periphery of the succeeding ring, and battle plates between said discs and said rings forming the sole means for holding said discs in fixed spaced relation with respect to said rings.

2. A muffiing device for engine exhaust gases including an entrance conduit, a series of spaced annularly cupped discs having their concave surfaces facing said entrance conduit, a series of annularly cupped rings, each having its concave surface facing the concave face of one of said discs, substantially funnel shaped members joining the outer periphery of each of said rings with the inner periphery of the succeeding ring, and radially offset baffle plates between said discs and said rings forming the sole means for holding said discs in fixed spaced relation to said rings and by means of which baffles a whirling motion is imparted to said exhaust gases in their passage through said muflling device.

3. In a mufiiing device having a cupped ring and a cupped disk adapted to be held in spaced concentric relation, exhaust gases being adapted to enter the opening of said ring to impinge on said disk and to flow substantially radially outward; a plurality of substantially fiat plates forming the sole means for holding said disk and ring in spaced relation, said plates being substantially parallel to and radially offset from the axis of said ring and disk for imparting a whirling motion to gas flowing therebetween.

CHARLES E. HATHORN. 

